Recently, in systems of optical communication technologies, effectiveness such as low loss of optical signals, broadband properties and operability is increasingly desired to be improved. It has been widely known that optical fiber connectors (also, called optical connector plugs) are utilized as connecting terminals for transmitting and receiving optical signals as such optical communication. When a problem such as an excessive light-receiving level of optical signals occurs owing to a short optical transmission distance, optical attenuators are commonly utilized for transmitting and receiving optical signals together with such the optical fiber connectors.
An optical fiber connector having a generally known structure was disclosed in FIG. 1 of Japanese Patent No. 3569488, for example. Such a connector includes housings which are constituted with a front plug body (i.e., a plug housing) and a rear extension cap as being integrally assembled in the front-rear direction, and a ferrule assembly equipped with a ferrule attached is accommodated at the inside thereof. The plug body includes key grooves (i.e., engagement openings) at opposite sides thereof, and the rear extension cap includes keys (i.e., engagement projections) formed at the respective sides corresponding to the engagement openings. The plug body and the rear extension cap are mechanically coupled by performing snap-fastening from the inside of the plug body between the engagement openings of the plug body and the engagement projections of the rear extension cap with sliding and engaging between the plug body and the rear extension cap.
Japanese Patent Application Laid-Open No. 2002-250840 shows in FIG. 1 an optical fiber connector in which a similar assembling manner with the housings of the optical fiber connector of Japanese Patent No. 3569488 is illustrated. Similarly to the above related art, an optical fixed attenuator of the embodiment disclosed in this related technology suggests in the same drawing mechanical join by snap-fastening between the engagement openings and engagement projections of two front and rear housings.
Drawings described later illustrate specific structural instance of snap-fastening structures which are adapted in the related art regarding the above conventional optical connectors. In this instance, optical connector plugs as optical fixed attenuators are illustrated.
Transformed examples of the optical connector plugs of the related art as the optical fixed attenuators which have a traditional snap-fastening structure are illustrated in FIGS. 6 and 7.
A front plug housing 31 has a quadrilateral cylinder or tubular shape and is molded with a resin such as polyetherimide (PEI). A latch 31a is disposed to the upper part thereof and openings to which a ferrule is inserted are formed respectively at front and rear sides of the cylinder. Here, a wall thickness at the openings of the front plug housing 31 is 0.45 mm. Engagement grooves, that is, engagement openings 31b, 31b, are formed respectively at both side surfaces of the cylinder. Meanwhile, a rear extension cap 32 has a quadrilateral engagement portion 32a having dimensions of a shape corresponding to the quadrilateral opening at the rear end of the front plug housing 31 at one side and an opening to accommodate an optical connector at the other side. Engagement projections 32d, 32d to be engaged respectively with the engagement openings 31b, 31b are integrally molded with the resin which is similar to the resin stated above, at both side surfaces 32c, 32c of the quadrilateral engagement portion 32a in a projected manner.
When a barrel ferrule assembly 33 to be an optical attenuator is accommodated in the front plug housing 31 and the quadrilateral engagement portion 32a of the rear extension cap 32 is assembled, snap-engagement is carried out between the engagement openings 31b, 31b and the engagement projections 32d, 32d, and both of the housings are mechanically and integrally coupled as illustrated in FIG. 7. During the coupling process of the both, the engagement projections 32d, 32d enter and widen elastically the quadrilateral openings of the front plug housing 31 from the inner surface thereof. Here, dust caps 34, 35 are disposed at the optical connector plug to protect ferrule end surfaces.